1. Field of the Invention
The present invention relates to a method for manufacturing an alternator driven by an internal combustion engine mounted to an automotive vehicle such as a passenger car or a truck, for example.
2. Description of the Related Art
FIG. 26 is a perspective of a stator of a conventional automotive alternator such as described in Japanese Patent No. 2927288, for example, FIG. 27 is a perspective showing a conductor segment used in the stator in FIG. 26, and FIGS. 28 and 29 are perspectives from a front end and a rear end, respectively, of part of the stator in FIG. 26.
This stator 300 includes: a stator core 301; a stator winding 302 wound onto the stator core 301; and insulators 304 mounted inside slots 303, the insulators 304 insulating the stator winding 302 from the stator core 301. The stator core 301 is a cylindrical laminated core laminated by stacking thin steel plates which are plate-shaped magnetic members, and has a number of slots 303 extending axially disposed at even pitch circumferentially so as to be open on an inner circumferential side. The stator winding 302 is constructed by joining a number of short conductor segments 305 in a predetermined winding pattern.
The conductor segments 305 are formed into a general U shape from an insulated copper wire material having a rectangular cross section, and are inserted from an axial rear end into pairs of slots 303 six slots apart (a pitch of one magnetic pole). Then, end portions of the conductor segments 305 extending outwards at a front end are joined to each other to constitute the stator winding 302.
More specifically, in pairs of slots 303 six slots apart, first conductor segments 305 are inserted from the rear end into first positions from an outer circumferential side within first slots 303 and into second positions from the outer circumferential side within second slots 303, and second conductor segments 305 are inserted from the rear end into third positions from the outer circumferential side within the first slots 303 and into fourth positions from the outer circumferential side within the second slots 303. Thus, within each slot 303, four straight portions 305a of the conductor segments 305 are arranged to line up in a row in a radial direction.
Then, end portions 305b of the conductor segments 305 extending outwards at the front end from the first positions from the outer circumferential side within the first slots 303 and end portions 305b of the conductor segments 305 extending outwards at the front end from the second positions from the outer circumferential side within the second slots 303 six slots away in a clockwise direction from the first slots 303 are joined to form an outer layer winding having two turns. In addition, end portions 305b of the conductor segments 305 extending outwards at the front end from the third positions from the outer circumferential side within the first slots 303 and end portions 305b of the conductor segments 305 extending outwards at the front end from the fourth positions from the outer circumferential side within the second slots 303 six slots away in a clockwise direction from the first slots 303 are joined to form an inner layer winding having two turns.
In addition, the inner layer winding and outer layer winding constituted by the conductor segments 305 inserted into the pairs of slots 303 six slots apart are connected in series to form one phase of the stator winding 302 having four turns.
A total of six phases of the stator winding 302 each having four turns are formed similarly. Then, two sets of three-phase stator winding portions are constructed by connecting three phases each of the stator winding 302 into alternating-current connections.
In the conventional stator 300 constructed in this manner, at the rear end of the stator core 301, turn portions 305c of the pairs of conductor segments 305 inserted into the same pairs of slots 303 are lined up in rows in a radial direction. As a result, the turn portions 305c are arranged in two rows circumferentially to constitute a rear-end coil end group.
At the front end of the stator core 301, on the other hand, joint portions formed by joining the end portions 305b of the conductor segments 305 extending outwards at the front end from the first positions from the outer circumferential side within the first slots 303 and the end portions 305b of the conductor segments 305 extending outwards at the front end from the second positions from the outer circumferential side within the second slots 303 six slots away, and joint portions formed by joining the end portions 305b of the conductor segments 305 extending outwards at the front end from the third positions from the outer circumferential side within the first slots 303 and the end portions 305b of the conductor segments 305 extending outwards at the front end from the fourth positions from the outer circumferential side within the second slots 303 six slots away are arranged to line up radially. As a result, joint portions formed by joining end portions 305b to each other are arranged in two rows circumferentially to constitute a front-end coil end group.
In the stator 300 of an automotive alternator having the above construction, because the stator winding 302 is constructed by inserting short conductor segments 305 formed in the general U shape into the slots 303 of the stator core 301 from the rear end and joining end portions 305b of the conductor segments 305 extending outwards at the front end, the coil end groups are composed of a large number of joint portions, allowing short-circuiting accidents to occur easily because the joint portions easily short-circuit with each other.
A large number of the short conductor segments 305 must be inserted into the stator core 301 and their end portions must be joined by welding, soldering, etc., making operability significantly poor. Furthermore, the amount of each conductor segment 305 which is inserted into the slots 303 must be greater than the length of the stator core 301, facilitating damage to the insulation and reducing the quality of the finished product. In addition, when joining the end portions, short-circuiting often occurs between the joint portions due to spilt solder or weld melt, making mass-producibility significantly poor.
In contrast to the conventional construction using conductor segments 305, Japanese Patent Laid-Open No. HEI 8-298756 discloses a stator construction consisting of a number of coil pieces formed by winding a number of straight-angled conductors a number of times into a generally hexagonal shape in advance and inserting the coil pieces into slots in semicircular divided core portions.
In this stator, the coil pieces are inserted into the slots of the semicircular divided core portions in order in a radially outward direction. In other words, first facing side portions of the hexagonal coil pieces are positioned in an inner circumferential layer which is a layer on the inner side of the slots, and second facing side portions are positioned in an outer circumferential layer which is a layer on the outer side a predetermined number of slots away.
In this stator, although the alignment of the coil ends extending outwards from the slots is good, when joining the divided core portions to each other, the first side portions of the coil pieces are already inserted into the slots of a first divided core portion but because it is necessary to perform the operation of inserting the coil pieces into the slots of a second divided core portion at the same time as the operation of connecting the divided core portions, a temporary holding jig or the like must be used to perform a complicated operation, making productivity significantly poor.
Forming the stator core by joining a number of divided core portions has also been troublesome, and forming the radial dimensions, etc., of each of the divided core portions so as to be uniform has been difficult.
Japanese Patent Laid-Open No. HEI 9-103052 discloses a stator 400 in which winding groups formed in a straight shape are inserted into a straight-shaped base core in a slot depth direction and the base core is bent into a cylindrical shape in a later process in order to improve the space factor of the conductors in the slots. FIG. 30 is an overall perspective of the stator 400 manufactured by this method. Although, insertion of the winding groups is significantly improved, because the winding groups have straight bridging portions extending circumferentially between the slots 401, the alignment of coil ends 402 extending outwards from the slots 401 is significantly poor, leading to increased radial dimensions and short-circuiting between the conductors in the coil ends 402. Furthermore, because the straight-shaped base core is made into a cylinder without modification, a significant amount of bending force is required and spring back is strong, leading to problems such as the formation of gaps at the joined surfaces in the resulting cylinder, and to deterioration in output and magnetic noise, etc.
In the conventional automotive alternator disclosed in Japanese Patent No. 2927288, problems have been that a large number of the short conductor segments 305 must be inserted into the stator core 301 and their end portions must be joined by welding, soldering, etc., making operability significantly poor, and when joining the end portions, that short-circuiting often occurs between the joint portions due to spilt solder or weld melt, making mass-producibility significantly poor.
In the alternator of Japanese Patent Laid-Open No. HEI 8-298756, problems have been that forming the stator core by joining a number of divided core portions has been troublesome, requiring a complicated operation using a temporary holding jig, thereby making the assembly operation of the stator poor.
In the automotive alternator disclosed in Japanese Patent Laid-Open No. HEI 9-103052, the alignment of coil ends 402 extending outwards from the slots 401 is significantly poor, leading to increased radial dimensions and short-circuiting between the conductors in the coil ends 402, and a significant amount of bending force is required to make the straight-shaped base core into a cylinder without special treatment, making spring back strong and leading to problems such as the formation of gaps at the joint surface in the resulting cylinder, deterioration in output and magnetic noise, etc.
The present invention aims to solve the above problems and an object of the present invention is to provide a method for manufacturing a mass-producible alternator for which the assembly operation is significantly improved.
To this end, according to the present invention, there is provided a method for manufacturing an alternator comprising: preparing a wire-strand group formed by bending said strands of wire so as to have straight portions which fit into said slots; forming a base core by laminating plate-shaped magnetic members formed with the slots; stacking said wire-strand group on said base core and pressing the wire-strand group such that the straight portions enter the slots; and forming the stator core by bending the base core into a cylindrical shape and abutting end surfaces of the base core.
According to another aspect of the present invention, there is provided a method for manufacturing an alternator comprising: preparing a wire-strand group formed by bending said strands of wire so as to have straight portions which fit into said slots; forming a base core by laminating plate-shaped magnetic members formed with the slots; stacking the wire-strand group on the base core and pressing the wire-strand group such that the straight portions enter the slots; forming the inner circumferential core portion by bending the base core into a cylindrical shape; and fitting the outer circumferential core portion over the inner circumferential core portion.